The present invention relates to a composition and method for controlling scarabs, especially lawn scarabs, utilising certain strains of the entomopathogenic nematode species Heterorhabditis zealandica. 
The family of beetles known as Scarabaeidae includes a number of species that are known as significant agricultural and horticultural pests. Larvae of lawn scarabs (such as Cyclocephala signaticollis, Heteronychus arator, Adoryphorus couloni, Antitrogus morbillosus, Anoplognathus porosus, Ataenius imparalis, Sericesthis geminata, S. pruinosus, S. nigrolineata, Scityla sericans, Saulostomus villosus, Aphodius tasmaniae, Heteronyx spp, Rhopoea magnicornis, Popillia japonica, Cyclocephala borealis, C. hirta, C. parallela, Melolontha melolontha, Anomala aenea, Phyllophaga phyllophaga, P. hirticula, Plyllopertha horticola, Haplididia etrusca, Maladea matrida, Costelytra zealandica, Amphimallon solstatialis, and Ligyrus subtropicus) feed on the roots of grasses thereby causing considerable damage to pastures, lawns and anmenity turf. Control treatments typically involve the use of chemical pesticide sprays, however these have a number of disadvantages. including low efficacy (particularly against final instar larvae), low specificity and public concern regarding pesticide residues. Consequently, there is a need for a viable alternative to the control of lawn scarabs by chemical pesticide spraying. In this regard, the present inventors have identified certain strains of the entomopatliogenic nematode species H. zealandica that are suitable for use as biological control agents for lawn scarabs.
Thus, in a first aspect, the present invention provides a composition for controlling a population of larval and/or pupal scarabs, comprising an amount of an entomopathogenic nematode optionally in admixture with a suitable agricultural and/or horticultural carrier, wherein said entomopathogenic nematode belongs to the species Heterorhabditis zealandica and has an LD50 value of less than 300 infective juveniles (IJ) as measured by pot assays against final instar scarab larvae.
Preferably, the entomopathogeniic nematode belongs to a strain of H. zealandica which has an LD50 value of less than 300 IJ as measured by pot assays against final instar Cyclocephlala signaticollis larvae and/or final instar Popillia japonica larvae.
More preferably, the entomopathogenic nematode belongs to a strain of H. zealandica which has an LD50 value of less than 175 IJ against final instar C. signaticollis larvae and/or final instar P. japonica larvae. Especially preferred are the strains designated JB1/X1, GKB and JB3D.
Compositions will include an amount of the entomopathogenic nematode which is, typically, about 50 to 10,000, more preferably about 500 to 1000, IJ/ml of composition.
Compositions will also typically include a suitable agricultural and/or horticultural carrier. Where the composition is desired to be in the form of an aqueous spray, the carrier may be selected from, for example, water or solutions in water of polyethylene glycol or glycerol or small quantities of wetting agent or various substances to stimulate nematode activity such as citric acid, insect blood or low concentrations of chemical pesticide. Where the composition is desired to be in a solid form, the carrier may be selected from, for example, calcium alginate and polyacrylamide (as would be suitable for gelled pellets), attapulgite or vermiculite (as would be suitable for solid granules), or other moist substrates such as peat, sponge, sawdust or cellulose. Compositions in solid form may be dispersed into an aqueous carrier (such as those mentioned above) for use as an aqueous spray.
Compositions are preferably stored at low temperature (e.g. 2 to 10xc2x0 C.) under aerobic conditions, and at a water activity of abpout Aw 0.97.
In a second aspect, the present invention provides a method for controlling a population of larval and/or pupal scarabs in an affected area, said method comprising applying to said area a composition in accordance with the first aspect.
For compositions in the form of aqueous sprays, application may be carried out with typical agricultural and/or horticultural spraying equipment including pressurised, fan sprayers venturi sprays and boom sprayers. For compositions to be applied in a solid form, application may be carried out with typical agricultural and/or horticultural scattering equipment such as those used for spreading fertilisers on lawn.
The composition will typically be applied to an affected area which has been subjected to heavy watering in amounts sufficient to provide 50,000 to 1 million IJ/m2, nmore preferably 100,000 to 500,000 IJ/m2. Following application, it is also preferable to submit the affected area once again to heavy watering in order to soak the composition into the root zone where the larval scarabs feed. Application of the composition is preferably conducted at dusk.
The composition and method of the invention may be used for the control of lawn scarabs (such as those mentioned above) and other pest scarabs (e.g. sugar cane scarabs, blueberry scarabs, etc.)
In a further aspect, the present invention provides a nematode, in a substantially purified form, selected from the H. zealandica strains designated JB1/X1, GKB and JB3D.
The term xe2x80x9ccontrollingxe2x80x9d as used herein in relation to a population of larval and/or pupal scarabs, is intended to refer to both maintaining (i.e. preventing increases) and reducing said population.
The terms xe2x80x9ccomprisexe2x80x9d, xe2x80x9ccomprisesxe2x80x9d and xe2x80x9ccomprisingxe2x80x9d as used throughout the specification are intended to refer to the inclusion of a stated step, component or feature or group of steps, components or features with or without the inclusion of a further step, component or feature or group of steps, components or features.